1. Field of the Invention
The present disclosure relates to a biometric authentication method, and more particularly, to a biometric authentication method which can enhance security.
This work was supported by the IT R&D program of MIC/ITA. [2007-S-020-01, Development of Privacy Enhanced Biometric System]
2. Description of the Related Art
Biometrics is a technology that proves an individual's identity using a user's physical/behavioral features. Examples of a biometric scheme using a physical feature include facial recognition, fingerprint recognition, iris recognition, etc, and examples of a biometric scheme using a behavioral feature include gait step recognition, signature recognition, etc. Generally, a biometric apparatus generates a template including the physical/behavioral features and uses the template for registering and identifying the user. A template which is registered and stored in the biometric apparatus is called a gallery or a registration template, and a template which is newly generated from a user upon authentication request is called a probe or an authentication template. User authentication compares the two templates and is achieved based on a comparison value generated through the comparison. For example, in a case where dissimilarity such as Euclidean distance is used as a comparison value, an authenticated user is classified as a genuine when the comparison value between two templates is less than a predetermined value, whereas the authenticated user is classified as an impostor when the comparison value between two templates is larger than a predetermined value. For another example, in a case where similarity such as a cosine function is used as a comparison value, an authenticated user is classified as a genuine when the comparison value between two templates is larger than a predetermined value, whereas the authenticated user is classified as an impostor when the comparison value between two templates is less than a predetermined value.
Since such biometric data include the unique information of each user, the privacy of each user can seriously be invaded when the biometric data is leaked and disclosed. Moreover, since the kind and number of data usable in biometrics are limited for each individual, for example each user has only one face and ten fingerprints, it is impossible to replace the lost data unless the each user undergoes a plastic surgery. Accordingly, once original data are leaked and stolen, damage due to this can be much larger than that of a case where a personal identification number is leaked.
Accordingly, in a case of data which are privacy-sensitive or important like biometric information, it is advised that encodes corresponding data using an encryption scheme. However, in a case of biometric data, although one and the same person's biometric information is obtained using the same device, it is impossible to get one and the same value every time. Moreover, although similar values are encrypted, the similar values are encrypted in different values due to the general characteristics of an encryption function. Ultimately, a comparison value, which is generated in a case where new input data are encrypted and the encrypted data are directly compared with data that are encrypted and registered in advance, are inconsistent with a comparison value generated in a case where an original type of data that are not encrypted are compared with each other. Accordingly, biometric authentication cannot directly use encrypted data for use authentication, and thus must decrypt encrypted data every time for comparison and authentication. That is, there is limitation in that a scheme of protecting an encrypted and registered template should decrypt the encrypted and registered template every time for data comparison and user-authentication, and consequently original data can be disclosed.
In particular, with advent of computer networks such as the Internet, important data are transmitted over the networks. Since the networks such as the Internet can easily be accessed by any user, critical vulnerability can occur in security. As an example, without hacking a client or a server directly, a personal identification number or a password is copied in the middle of being transmitted over the Internet and thereafter can be used to gain an illegal access to a server by retransmitting the copied data to a server. In this case, although secret information is encrypted, irrespective of whether original secret information is derived from the encrypted information, the encrypted secret information is copied and stored in the middle and thereafter is retransmitted as it is, thereby authenticating a user. Accordingly, in a case where data transmitted over a network are biometric information, as described above, vulnerability in security can be far more serious and threatening.